Electric motor



28, 1934. sc c 1,971,506

ELECTRIC MOTOR Filed Sept. 25, 1931 INVENTOR A'ITORNE Patented Aug. 28, 1934 UNITED STATES PATENT O'FFICZE ELECTRIC MOTOR Application September 25, 1931, Serial No. 565,016

2 Claims.

This invention relates to an electric motor and particularly the make-and-break device which alternately opens the field member of the motor. This device is operated from the armature shaft of the armature which is rotated by the alternate energizing of the field member.

The object of the invention is to provide a motor having increased power over those employing the usual contact actuating device as the new device breaks the contact quicker and this allows the current to flow for a longer period.

Another advantage is that the contact device cuts down arcing due to this quick break and this in turn reduces the heat. For this reason the motor is particularly adapted for use in enclosed places such as the handles of electrically operated hand tools in which the motor is located in the handle.

The invention also provides a cooler motor as the contact can be arranged in close proximity to the armature which acts as a fan to assist in cooling the contact device and circulating the air in its vicinity.

.The invention provides two movable contacts which are movable on attaching elements and function accurately even under slight loosening of the supporting means or a slight disarrangement of the contact arms. This is due to a flexibility around the centre of the armature shaft or other actuating device in contrast to the old construction comprising a fixed contact and movable contact. This latter construction requires accurate adjustment and in small motor distortion due to heat or a wearing of the contact destroys or affects the efficiency of the motor. With two movable contacts, as in this present invention, these difiiculties are overcome.

The invention is an improvement on motors as illustrated and described in my application for Letters Patent No. 476,303, filed August 19, 1930.

This invention is illustrated in the accompanying drawing in which Figure 1 is a top view of a motor of my improved construction shown in the handle of a hand tool with the cover of the handle removed. Figure 2 is a section on line 22 in Figure 1. Figure 3 is a section without the casing on line 3-3 in Figure 2. Figure 4 is a section of the motor field member and the armature in a reduced scale, the section being taken on a plane indicated by line 4-4 in Figure 1.

In the drawing 10 indicates the main part of a handle and 11 is the cover. The motor comprises a V-shaped field member 12 and an armature 13 rotatable between the ends of the field member and fixed on a shaft 14 which extends from the casing 10 for attachment to any desired tool or implement. The field member is provided with a coil 15 connected with the wire 16 of the feed wires and with the contact device by wire 17. The contact is connected by wire 18 with the other feed wire 19. The contacts are operated from the shaft 14 and I show the cam 20 as such operating means.

The contact device comprises two movable contact supports such as the arms 21 and 22 of insulating material and I show them as hinged at 23 to the base or bracket 24 secured by screws 25 to the casing 10. The ears 26 are struck up as bearings for the pin 23 of the hinge.

The contact points 27 and 28 are fastened to clips 29 and 30 respectively and fastened to the ends of the arms 21 and 22 by screws 31. The clips 29 and 30 are preferably formed with a broad. face 33 and pins or points 34 for dissipating heat from the arcing that takes place when the contacts separate. It will be noted that the arms 21 and 22 are spaced apart by the cam 20 and are held in position in a yielding manner by the spring 35 which is preferably U-shaped and rests on the bracket between the ears 26 and needs no other fastening.

With this construction the two movable contacts are operated simultaneously by the cam 20. The break in the circuit is quick with the result that the current is on longer and more power is given to the field to force the rotation of the armature 13. Any slight disarrangement of the pivot 23 through minor defects in the bracket or hinge will not affect the proper and synchronous movement of the contacts. Furthermore, any slight error in the location of the major or minor axis of the cam 20 does not affect the timing of the contact break. The quick break due to both contacts retreating simultaneously minimize the arcing and thereby cause no high temperature of the contact points and theylast longer.

The contacts are placed in close proximity to the armature which acts as a fan to circulate the air and tends to keep the contacts cool, thereby avoiding excess heat in the handle which can be made imperforate to keep out dust and V tion and operation of the parts without departing from the scope of the invention.

The speed of the motor can be altered by changing the leverage on the arms 21 and 22. The distance between the pivot 23 and the cam 20 and its ratio to the distance from the cam 20 to the contacts 27 and 28 regulates the duration of contact and therefore the speed of the motor.

I claim:-

1. A contact device comprising a bracket having ears to provide a bearing, a pair of arms having knuckles hinged together and to the ears,

JACOB SCHICK. 

